The overall objectives are to understand the molecular structure of visual photoreceptors, the dynamics of the molecular components and the mechanism of visual sensory transduction. The current goal is to understand the structure of the rod outer segment disk membrane and to learn how it functions. Low angle X-ray diffraction and colorimetric indicators of calcium and proton concentration will be coupled with flash photolysis to investigate structural and potential functional responses on a physiologically relevant time scale. The proteolytic fragmentation pattern of rhodopsin will be investigated on the surface of the membrane which is on the inside of the disk in the native state. The X-ray diffraction of the enzymatically altered membranes will be investigated. Work will be completed using covalent imidoester labeling reagents to explore the transmembrane asymmetry of protein and lipid groups. New, more reactive imidoester covalent cross-linking reagents will be developed. The lipid-lipid and lipid-protein interactions in the disk membrane will be studied with proton and carbon-13 NMR and a fluorescent fatty acid probe, parinaric acid. BIBLIOGRAPHIC REFERENCES: Farnsworth, C. C. and E. A. Dratz, Oxidative Damage of Retinal Rod Outer Segment Membranes and the Role of Vitamin E. Biochim. Biophys. Acta, 443, 556-570 (1976). Brown, M. B., G. P. Miljanich and E. A. Dratz, Proton NMR Evidence for Lipid-Rhodopsin Interaction in Rod Outer Segment Membranes, FEBS Lett., 70, 56-60 (1976).